Oil viscosity seems the most likely culprit. For a digital it makes no difference. Or an analogue without a seconds hand, I suspect: the hour and minute hands moving so slowly so as not to meet much resistance.

But a quartz analogue watch has minimal torque, so I imagine viscosity is the issue. There were several different types of oil available in the shop, but only one 'silicon oil'. This is what others had used, so I thought I'd try it. But likely I need to research it a bit more. Posting the failure anyway in case useful to others.

At least the patient recovered. This watch has had a hard life.